Physcia caesia is characterized by the blueish globular soralia in the thallus centre. The very similar P. subalbinea produces soralia at the lobe ends. It is primarily saxicolous on various types of enriched substrates. It is common on anthropogenic stands (walls, roofs, etc.) and on various calcareous substrates. On acidic silicates the lichen may occur at places enriched with bird droppings. It prefers well-lit and exposed sites. The species may rarely also occur on trees, mainly at bases and at dusty places. Its distribution area covers most of Europe. It is a common lichen in Europe and in the Czech Republic.taxonomic classification:
All records: 219, confirmed 151. One click on a selected square displays particular record(s), including their source(s).